Evaporator heat exchanger

ABSTRACT

An evaporator heat exchanger for evaporating a liquid working medium may include a housing, in which at least one first flow channel for conducting the working medium and at least one second flow channel for conducting a gas may be arranged, where heat may be transferable from the gas to the working medium. The evaporator heat exchanger may also include a plurality of cover plates and a profiled fluid plate arranged in between two of the cover plates. The at least two cover plates and the profiled fluid plate may form the at least one first flow channel, and at the same time may delimit at least one of at least one leakage channel and a leakage space that is separated from the at least one first flow channel and at least one second flow channel.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a US National Phase application of International Patent Application PCT/EP2013/066248, filed on Aug. 2, 2013, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to an evaporator heat exchanger for evaporating liquid working medium.

BACKGROUND

In order to further lower the fuel consumption in commercial vehicles and passenger cars, attempts are made to recover a part of the energy of the exhaust gas. This can take place thermally, i.e. the energy of the exhaust gas is used for example to heat a passenger compartment or to heat the internal combustion engine or the transmission. In a variant that has been discussed for some time, although thermal energy is removed from the exhaust gas, said thermal energy is returned to the internal combustion engine in a mechanical form. This method is based on a steam power process, in which a particular working medium is evaporated and superheated in an evaporator and is expanded in an adjoining expander, for example a turbine, with the result that mechanical energy is generated. The evaporation takes place here by means of heating via the exhaust gas. The working medium to be evaporated is in this case usually first heated up to boiling point in an evaporator, then evaporated and subsequently superheated. This can take place in principle at two different locations in a motor vehicle. Firstly, heat can be withdrawn from the exhaust gas in an evaporator, which is used instead of an exhaust gas cooler, in order to evaporate the working medium. In this case, the exhaust gas is cooled by the evaporation of the fluid to be evaporated and is then fed back to the motor together with the fresh air. Secondly, the main exhaust gas flow is also intended to be used as a heat source, in order likewise to evaporate working medium here in what is known as a main exhaust gas evaporator. Such a main exhaust gas evaporator is usually arranged by the vehicle manufacturers after the silencer or after the entire exhaust gas aftertreatment device in the exhaust gas system. Alternatively, the charge air in supercharged engines is used as a heat source.

WO 2012/010349 A1 discloses a generic evaporator heat exchanger for evaporating liquid working medium and for using waste heat from an internal combustion engine. In the known system, introduction of the working medium into the combustion air fed to the internal combustion engine on account of a sealing problem or leakage in the evaporator heat exchanger is intended to be substantially ruled out. To this end, at least one first flow channel is formed by at least one first delimiting component and at least one second flow channel is formed by at least one second delimiting component, wherein there is a fluid-conducting connection into the surroundings or into a receiving chamber from at least one of these delimiting components, such that in the event of a leakage at the delimiting components, the working medium is introducible into the surroundings or into the receiving chamber.

Concepts of a gas-operated evaporator heat exchanger that are described in the prior art provide for the risk of gas and working medium mixing to be reduced. If for example a fluorinated refrigerant flows into the exhaust gas and is fed together therewith into the internal combustion engine and combusted therein, hydrofluoric acid is produced, and this can pass out of the exhaust pipe and cause damage there. If, rather than this refrigerant, use is made for example of an alcohol, in the event of a leakage, the alcohol would be co-combusted in the internal combustion engine, and this would become noticeable on account of a sudden increase in power of the internal combustion engine. Under certain circumstances, this may be manageable only with difficulty, in particular for inexperienced drivers.

SUMMARY

Therefore, the present invention deals with the problem of specifying an improved embodiment for an evaporator heat exchanger of the generic type, in which undesired mixing of working medium and gas, in particular exhaust gas or charge air, can be ruled out.

This problem is achieved according to the invention by way of the subject matter of the independent claim. Advantageous embodiments are the subject matter of the dependent claims.

The present invention is based on the general idea of providing a leakage channel and/or leakage space between a first flow channel that conducts working medium and a second flow channel that conveys gas, in particular exhaust gas or charge air, and in the process of configuring both the first flow channel and the leakage channel and/or the leakage space with a particularly simple structure by way of two cover plates and a profiled fluid plate arranged in between. The evaporator heat exchanger according to the invention for evaporating liquid working medium in this case has a housing in which said first flow channel for conducting the working medium and the second flow channel for conducting the gas are arranged. By way of heat transfer from the gas, for example charge air or exhaust gas, to the working medium, the latter is evaporated, with the result that it can subsequently be expanded in an expansion machine, for example in a turbine, and as a result exerts mechanical work. As mentioned, according to the invention, the first flow channel and at least one leakage channel and/or leakage space are formed by two comparatively thick cover plates and a profiled fluid plate arranged in between, wherein a plate pack formed from two cover plates and a fluid plate located in between thus accommodates the first flow channel and the at least one leakage channel and/or leakage space fluidically separated therefrom. The connection between the two cover plates and the fluid plate arranged in between is produced in a cohesive manner, for example via a soldered connection. Arranged in this case between two adjacent plate packs is in each case a second flow channel through which the heat transfer gas, for example exhaust gas or charge air, flows. If the fluid plate breaks and/or if the soldered seam between the fluid plate and the cover plate fails, the working medium passes from the first flow channel into the leakage channel and/or into the leakage space and can be discharged from there without being directly mixed with the gas, for example exhaust gas, flowing through the second flow channel. In the same way, the leakage channel and/or the leakage space can also be used to discharge gas passing undesirably out of the second flow channel, if for example detaching of a soldered connection between the fluid plate and the cover plate or breaking of a wall of the fluid plate would result in a fluidic connection between the leakage channel and the second flow channel. As a result of this, too, gas now flowing into the leakage channel and/or into the leakage space can be discharged and as a result direct mixing with the working medium in the first flow channel can be avoided. The leakage channel and/or leakage space thus forms a natural safety barrier located between the two flow channels. The leakage channel and/or the leakage space is usually filled with air.

Expediently, the strength of a material of the fluid plate is less than the strength of a cover plate arranged on the fluid plate. This brings about a kind of predetermined breaking point of the fluid plate, such that if the evaporator heat exchanger is overloaded in the region of the first flow channel, the working medium conducted through the first flow channel passes into the leakage channel. If, for example, the fluid plate breaks, the cover plate delimiting the first flow channel expands under certain circumstances and compresses the rib structure arranged for example in the second flow channel. During the expansion of the cover plate, a soldered seam connecting the fluid plate to said cover plate can be detached, with the result that a fluidic connection between the first flow channel and the leakage channel is created. From the latter, the working medium can be discharged without mixing with the gas flowing through the second flow channel. In the same way, such a predetermined breaking point can also be formed by a smaller wall thickness or material thickness of the fluid plate compared with the cover plates connected thereto. What is important here is always that, in the event of an overload, first of all the fluid plate breaks or ruptures and not the cover plates. In this way, regardless of the type of failure, it is always possible to ensure that the leakage channel and/or leakage space located between the first and the second flow channel can be used to discharge the working medium or the gas. The leakage channel and leakage space are preferably impressed in an encircling manner in the fluid plate, wherein larger areas are denoted leakage space and smaller areas are denoted leakage channel.

In a further advantageous embodiment of the solution according to the invention, the evaporator heat exchanger has a plurality of plate packs stacked on top of one another with in each case a second flow channel arranged in between, wherein the leakage channel and/or the leakage space in a fluid plate has a first opening and a plurality of cover plates, arranged opposite one another, of two adjacent plate packs each have a second opening, wherein a leakage bushing for forming a (leakage) outlet duct, is arranged between the second openings. In this way, the leakage fluid or gas can be reliably drained from the second flow channel or the working medium can be reliably drained from the first flow channel.

In an advantageous development of the solution according to the invention, the housing has a housing opening which is connected, via a housing leakage bushing, to the first or second opening in the cover plate of a plate pack arranged adjacent to the housing. In this case, the housing leakage bushing and all further leakage bushings form an outlet duct, also known as a leakage outlet duct, for conducting the leakage fluid, wherein a line into the surroundings or periphery is attachable to the housing leakage bushing, a sensor which is configured to measure the pressure and/or the flow rate and/or a chemical composition of the fluid in the line being arranged in the region of said line. Ambient air pressure usually prevails in the outlet duct. At the same time air with the usual quality is present. If, on account of an overload, the fluid plate breaks or ruptures and thus working medium passes out of the first flow channel or gas passes out of the second flow channel into the leakage channel, then the pressure, the temperature and/or the chemical composition changes therein, since the leakage fluid, regardless of whether it is exhaust gas or working medium, has different physical and/or chemical properties than air. If a corresponding change indicating a leakage is detected by the sensor, then the latter can for example control a pump delivering the working medium or an exhaust gas recirculation valve depending on the signal detected by the sensor. It is likewise conceivable for a warning signal, which visually and/or acoustically notifies a user of the motor vehicle of a malfunction in the evaporator heat exchanger, to be output. Ambient air pressure of about 1 bar is usually present—as described above—at the sensor. If the evaporator heat exchanger is put into operation, the pressure in the leakage channel and/or in the leakage space rises to about 1-1.5 bar on account of the temperature-related expansion, this being normal. However, if the pressure does not rise, then either the sensor is defective or the leakage channel and/or leakage space has a sealing problem via which a drop in pressure can occur. If the pressure rises considerably during operation of the evaporator heat exchanger, this usually indicates a leakage of the first flow channel or of the second flow channel. The operation of the leakage channel is thus tested each time the motor vehicle is restarted, in particular upon each cold start.

Further important features and advantages of the invention can be gathered from the dependent claims, from the drawings, and from the associated description of the figures with reference to the drawings.

It goes without saying that the abovementioned features and those yet to be explained in the following text are usable not only in the combination given in each case but also in other combinations or on their own, without departing from the scope of the present invention.

Preferred exemplary embodiments of the invention are illustrated in the drawings and are described in more detail in the following description, wherein identical reference signs refer to identical or similar or functionally identical components.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures, in each case schematically,

FIG. 1 shows a view of an evaporator heat exchanger according to the invention,

FIG. 2 shows a sectional illustration through the evaporator heat exchanger in the region of first and second flow channels in the intact state,

FIG. 3 shows an illustration as in FIG. 2 but with the fluid plate broken and working medium passing into a leakage channel,

FIG. 4 shows an illustration as in FIG. 3, but with gas passing from the second flow channel into the leakage channel,

FIG. 5 shows a possible embodiment of the fluid plate according to the invention,

FIG. 6 shows an exploded illustration of the evaporator heat exchanger,

FIG. 7 shows a sectional illustration through the evaporator heat exchanger in the region of the fluid inlet or outlet,

FIG. 8 shows an illustration as in FIG. 7, but in the region of an outlet duct for leakage fluid,

FIG. 9 shows a pressure/time diagram with different curves which indicate different operating states or leakages of the evaporator heat exchanger according to the invention.

DETAILED DESCRIPTION

According to FIG. 1, an evaporator heat exchanger 1 according to the invention for evaporating liquid working medium 2 (cf. also FIGS. 2 to 4) has a housing 3 in which a first flow channel 4 for conducting the working medium 2 and a second flow channel 5 for conducting a gas 6 are arranged. The working medium 2 is heated in this case by heat transfer from the gas 6, for example from exhaust gas or charge air. According to the invention, the first flow duct 4 is now formed by two cover plates 7 and 8 and a profiled fluid plate 9 arranged in between, wherein the fluid plate 9, together with the two cover plates 7 and 8, at the same time delimits at least one leakage channel 10 and/or leakage space 11 that is separated from the two flow channels 4, 5. The two cover plates 7, 8 form, together with a fluid plate 9 arranged in between, a plate pack 12, as is illustrated for example in FIGS. 2 to 4. The respective leakage channel 10 and the leakage space 11 are in this case arranged laterally next to or at the periphery of the first flow channel 5, as can be gathered in particular also from FIG. 5.

The leakage channel 10 according to the invention creates a barrier between the two flow channels 4, 5, such that it is not possible for the working medium 2 to mix directly with the gas 6 and as a result to damage an internal combustion engine. In the case of evaporator heat exchangers that are known from the prior art, the working medium to be evaporated flows into the exhaust gas in the event of a leakage and can, if for example a fluorinated refrigerant, for example R245fa, is used, be combusted in the internal combustion engine, thereby producing poisonous hydrofluoric acid. This would pass out of the exhaust pipe and cause damage there. If, rather than such a refrigerant, use is made of alcohol, for example ethanol or methanol, in the event of a leakage, the latter would be co-combusted in the internal combustion engine, and this would be reflected in a sudden increase in power of the internal combustion engine. In particular inexperienced drivers would be exposed to an increased risk of an accident as a result. However, as a result of the barrier according to the invention of the leakage channel 10 and leakage space 11 type, in the event of virtually any kind of failure of the fluid plate 9, mixing of the gas 6 with the working medium 2 can be reliably prevented.

In addition to the provision of the leakage channel 10 and/or of the leakage space 11 (cf. also FIG. 5) the strength of the material for the fluid plate 9 is less than the strength of the cover plates 7, 8 connected to the fluid plate 9, such that the fluid plate 9 generally represents a kind of predetermined breaking point in the system of the plate pack 12. In a similar manner, such a predetermined breaking point can also be realized by a smaller wall thickness or material thickness of the fluid plate 9 compared with the wall thickness or material thickness of the cover plates 7, 8.

In FIG. 2, the evaporator heat exchanger 1 is in this case shown in a normal operating state in which gas, in particular exhaust gas, flows through the second flow channel 5 and transfers heat to the working medium 2 in the first flow channel 4. For better heat transfer, a rib structure 13 can be arranged in this case in the second flow channel 5, i.e. between two plate packs 12. A connection of the fluid plate 9 to the two cover plates 7, 8, or a connection of the rib structure 13 to the respective cover plates 7, 8, is produced in this case preferably in a cohesive manner, for example via a soldered connection 14.

FIG. 3 now shows a case of failure of the fluid plate 9, in which the central fluid plate 9 has broken and as a result has resulted in deformation or upward bending of the more strongly dimensioned cover plate 7. The deformation of the cover plate 7 in turn results in detaching of the soldered connection 14, with the result that the working medium 2 present in the first flow channel 4 can flow into the leakage channel 10. A fluidic connection with the second flow channel 5 and thus with the gas 6 does not occur.

FIG. 4 shows a case in which the fluid plate 9 has likewise broken on account of an overload and in the process has created a fluidic connection between the second flow channel 5 and the leakage channel 10. The gas 6 passing out of the second flow channel 5 can in this case be discharged via the leakage channel 10 without mixing with the working medium 2 in the first flow channel 4. In both of the cases of failure that are shown in FIGS. 3 and 4, undesired mixing of the working medium 2 with the gas 6 and the resulting difficulties is thus reliably avoided.

Considering the fluid plate 9 according to FIG. 5, the first flow channel 4 and the leakage channel 10 extending at the periphery and leakage spaces 11 located in between can be seen very clearly. A fluid infeed 15 and a fluid drain 16, via which working medium 2 can be fed to the fluid plate 9 and discharged therefrom again can likewise be seen. Likewise, the fluid plate 9 has a first opening 17 via which the leakage channel 10 and the leakage space 11 are connected to a (leakage) outlet duct 18 (cf. FIG. 1). A plurality of cover plates 7, 8, arranged opposite one another, of two adjacent plate packs 12 additionally each have a second opening 19, wherein a leakage bushing 20 for forming the outlet duct 18, in particular the leakage outlet duct 18, is arranged between two second openings 19. In the case of an assembled plate pack 12, the first openings 12 are thus aligned with the second openings 19 and the leakage bushings 20 and as a result form the outlet duct 18.

Considering FIG. 6 further, it can be seen that the cover plates 7, 8 each have a third opening 21 for conducting the working medium 2 through the first flow channel 4, wherein the third openings 21 are connected together, between mutually opposite cover plates 7, 8 of two adjacently arranged plate packs 12, in each case by a fluid bushing 22, and the fluid bushing 22 has an at least partially encircling fluid bushing annular channel 23 that is separated from the first flow channel 4, said fluid bushing annular channel 23 being connected to the leakage channel 10 and/or the leakage space 11 in the fluid plate 9 of the plate pack 12. As a result, it is likewise possible to create a safeguard against working medium 2 passing undesirably out of the fluid bushings 22. The third openings 21 in this case form a corresponding fluid feed duct 24 and fluid drain duct 25 together with the fluid bushings 22 arranged in between and the fluid infeed 15 and fluid drain 16, arranged in a manner aligned therewith, in the fluid plates 9.

FIG. 7 shows a sectional illustration through the evaporation heat exchanger 1 according to the invention in the region of the fluid feed duct 24 and of the fluid drain duct 25. The uppermost fluid bushing 22 is in this case welded to the housing 3 in a fluid-tight manner via a welded connection 26. Between in each case two adjacent fluid bushings 22, a plate pack 12 having two cover plates 7, 8 and a fluid plate 9 arranged or soldered in between can be seen.

FIG. 8 shows a sectional illustration through the evaporation heat exchanger 1 according to the invention in the region of the outlet duct 18, wherein the uppermost leakage bushing 20 is again welded to the housing 3 in a fluid-tight manner via a welded connection 26. The individual plate packs 12 again consisting of the two cover plates 7, 8 and the fluid plate 9 arranged in between are in this case soldered both together and to the individual leakage bushings 20 in a fluid-tight manner via a respective soldered connection 14. The uppermost leakage bushing 20 is in this case also referred to as the housing leakage bushing 27. The housing leakage bushing 27 is adjoined by a line 28 (cf. FIG. 1) into the surroundings or the periphery, said line 28 continuing outside the evaporator heat exchanger 1. In the line 28 or the outlet duct 18, provision can be made of a sensor 29 which is configured to measure the pressure and or the flow rate and/or a chemical composition of the fluid in the line 28, i.e. in particular also in the leakage channel 10 or in the outlet duct 18.

Provision can likewise be made of an open-loop and/or closed-loop control device 30 which is configured to evaluate a signal detected by the sensor 29, in particular the pressure, the flow rate and/or the chemical composition of the fluid, in particular of the leakage fluid, in the line 28, and for the open-loop/closed-loop control of a pump (not shown) delivering the working medium and/or of an exhaust gas recirculation valve (likewise not shown) depending on the signal detected.

The ambient air pressure of about 1 bar is usually present at the sensor 29, as long as the evaporator heat exchanger 1 is switched off and is at ambient temperature. This is shown in FIG. 9 by way of the curve A. If the evaporator heat exchanger 1 is put into operation, the pressure within the line 28 and within the leakage channels 10 rises to about 1 to 1.5 bar on account of the temperature-related expansion of the air, this being illustrated in FIG. 9 by way of the curve B. If the evaporator heat exchanger 1 is put into operation and the pressure does not rise, this likewise being shown in FIG. 9 by way of the curve A, either the sensor 29 is defective or the line 28 and the leakage channel 10 have a leak. In the event of a leakage in the fluid plate 9, the pressure rises considerably when the working medium 2 passes into the leakage channel 10, this being illustrated in FIG. 9 by way of the curve C, and somewhat less when the fluid plate 9 ruptures in the direction of the second flow channel 5 and thus gas 6 passes into the leakage channel 10, this being illustrated in FIG. 9 by way of the curve D. Generally, the operation of the leakage channel 10 can be tested each time the internal combustion engine or the system is restarted, with the result that high operational reliability can likewise be ensured. In addition, it is immediately possible to draw conclusions about the type of failure from the curve profile.

In general, the evaporation heat exchanger 1 according to the invention has the following advantages:

avoidance of undesired mixing of the working medium 2 with the gas 6, for example exhaust gas or charge air,

no health risk when refrigerant is used,

no safety risk when alcoholic working medium 2 is used,

ongoing testability of the function of the leakage concept. 

1. An evaporator heat exchanger for evaporating a liquid working medium, comprising: a housing, in which at least one first flow channel for conducting the working medium and at least one second flow channel for conducting a gas are arranged, heat being transferable from the gas to the working medium; and a plurality of cover plates and a profiled fluid plate arranged in between two of the cover plates; wherein the at least two cover plates and the profiled fluid plate form the at least one first flow channel and at the same time delimit at least one of (i) at least one leakage channel and (ii) a leakage space that is separated from the at least one first flow channel and the at least one second flow channel. 2.-11. (canceled)
 12. The evaporator heat exchanger of claim 1, wherein the at least one of (i) the at least one leakage channel and (ii) the leakage space is arranged laterally at least one of next to and at a periphery of the at least one first flow channel.
 13. The evaporator heat exchanger of claim 1, wherein at least one of: a strength of a material of the profiled fluid plate is less than a strength of a material of at least one of the cover plates arranged on the profiled fluid plate; and the profiled fluid plate has a smaller wall or material thickness than at least one of the cover plates arranged on the profiled fluid plate.
 14. The evaporator heat exchanger of claim 1, wherein two cover plates with a profiled fluid plate arranged in between form at least one plate pack, said plate pack having at least one leakage channel encircling at least partially in a peripheral region of the plate pack.
 15. The evaporator heat exchanger of claim 14, further comprising a plurality of plate packs stacked on top of one another with a second flow channel arranged between adjacent plate packs, the profiled fluid plate in each plate pack having a first opening in at least one of a leakage channel and a leakage space, wherein cover plates of adjacent plate packs opposite one another each have a second opening between which a leakage bushing for forming an outlet duct is arranged.
 16. The evaporator heat exchanger of claim 15, wherein the first opening is connected directly to the leakage bushing.
 17. The evaporator heat exchanger of claim 15, wherein the cover plates each has a third opening for conducting the working medium through the first flow channel, the third openings being connected together, between mutually opposite cover plates of two plate packs arranged adjacent to one another, by a fluid bushing, the fluid bushing having an at least partially encircling fluid bushing annular channel that is separated from the first flow channel, said fluid bushing annular channel being connected to the at least one of a leakage channel and a leakage space in the profiled fluid plate of the plate packs.
 18. The evaporator heat exchanger of claim 15, wherein the housing has a housing opening which is connected via a housing leakage bushing to at least one of the first opening and the second opening in the cover plate of the plate pack arranged adjacent to the housing.
 19. The evaporator heat exchanger of claim 18, wherein the housing leakage bushing and a plurality of leakage bushings between the cover plates of adjacent plate packs form the outlet duct for conducting the fluid, wherein a line into external to the housing is attachable to the housing leakage bushing, said line having a sensor configured to measure at least one of a pressure, a flow rate, and a chemical composition of a fluid in the line.
 20. The evaporator heat exchanger of claim 14, wherein at least one of: a rib structure is arranged in each of the second flow channels between adjacent plate packs; and for each plate pack, the profiled fluid plate is at least one of soldered and welded between two cover plates.
 21. The evaporator heat exchanger of claim 19, further comprising a control device configured to evaluate a signal detected by the sensor for the control of at least one of a pump delivering the working medium and an exhaust gas recirculation valve depending upon the signal detected.
 22. The evaporator heat exchanger of claim 2, wherein at least one of: a strength of a material of the profiled fluid plate is less than a strength of a material of at least one of the cover plates arranged on the profiled fluid plate; and the profiled fluid plate has a smaller wall or material thickness than at least one of the cover plates arranged on the profiled fluid plate.
 23. The evaporator heat exchanger of claim 2, wherein two cover plates with a profiled fluid plate arranged in between form at least one plate pack, said plate pack having at least one leakage channel encircling at least partially in a peripheral region of the plate pack.
 24. An evaporator heat exchanger for evaporating a liquid working medium, comprising: a housing; and a plurality of plate packs arranged in the housing one on top of another, each plate pack having two cover plates with a profiled fluid plate arranged in between to form a first channel for conducting the working medium, and at the same time delimiting at least one of at least one leakage channel and a leakage space separated from the first flow channel; wherein a second flow channel for conducting a gas is arranged in between adjacent plate packs.
 25. The evaporator heat exchanger of claim 24, wherein each plate pack has a first opening in at least one of a leakage channel and a leakage space, and the cover plates of adjacent plate packs opposite one another each have a second opening between which a leakage bushing for forming an outlet duct is arranged.
 26. The evaporator heat exchanger of claim 25, wherein the cover plates each has a third opening for conducting the working medium through the first flow channel, the third openings being connected together, between mutually opposite cover plates of two plate packs arranged adjacent to one another, by a fluid bushing, the fluid bushing having an at least partially encircling fluid bushing annular channel that is separated from the first flow channel, said fluid bushing annular channel being connected to the at least one of a leakage channel and a leakage space in the fluid plate of the plate packs.
 27. The evaporator heat exchanger of claim 25, wherein the housing has a housing opening which is connected via a housing leakage bushing to at least one of the first opening and the second opening in the cover plate of the plate pack arranged adjacent to the housing.
 28. The evaporator heat exchanger of claim 25, wherein the housing leakage bushing and a plurality of leakage bushings between the cover plates of adjacent plate packs form the outlet duct for conducting the fluid, wherein a line into external to the housing is attachable to the housing leakage bushing, said line having a sensor configured to measure at least one of a pressure, a flow rate, and a chemical composition of a fluid in the line.
 29. The evaporator heat exchanger of claim 24, wherein at least one of: a rib structure is arranged in each of the second flow channels between adjacent plate packs; and for each plate pack, the fluid plate is at least one of soldered and welded between two cover plates.
 30. The evaporator heat exchanger of claim 28, further comprising a control device configured to evaluate a signal detected by the sensor for the control of at least one of a pump delivering the working medium and an exhaust gas recirculation valve depending upon the signal detected. 